Listen for GPU hotplug events to initialize their cursor support.
This fixes one reason for why DisplayLink devices may not be using a hardware
cursor. Particularly, when a DisplayLink device is hotplugged for the first
time such that EVDI creates a new DRM device node after gnome-shell has already
started, we used to forget to initialize the cursor support.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/1097
(cherry picked from commit 8abdf16a3992e3332f2378ea7c65e6e251e418e0)